Strainer mechanism for use in continuous cooking of chips in the manufacture of pulp



June 8, 1954 D. N. OBENSHAIN 2,580,684

STRAINER MECHANISM FOR USE IN CONTINUOUS COOKING 0F CHIPS IN THE MANUFACTURE OF PULP Filed Dec. 6, 1951 3 Sheets-Sheet 1 E ea I b j 3 ,F /3 1 ll 7 c 7 E K 5 Y,

E g I7 9 5 lb 5 a a Q k g kg 70 BLOW VALVE k F/@ I June 8, 1954 D, N. OBENSHAIN 2,680,684

STRAINER MECHANISM FOR USE IN CONTINUOUS COOKING OF CHIPS IN THE MANUFACTURE OF PULP 3 Sheets-Sheet 2 Filed Dec. 6, 1951 Gttornegs June 8, 1954 D. N. OBENSHAIN 2,680,684

STRAINER MECHANISM FOR USE IN commuous COOKING OF CHIPS IN THE MANUFACTURE OF PULP 3 Sheets-Sheet 3 Filed Dec. 6, 1951 Gttorncgs Patented June 8, 1954 .ISZI RAINER- MECHANISM. FOR" USE IN CON- TTINUOU S T COOKING Ii OF .IICHIPSIN.QTHE

FA'CTURE OF PULP ai -David Noel' Obenshain, .Piedmont lw. Va.', as- -s z signor dozwest :Virginia Pulp'zantf Bauer Gompanyi-New York; N:Y.-; a; corporation ot-Dela- 1: "Vare Aliplicatioii Deceinber 6, il-951 serial N 61*26 012 7 a8 Claims. I

my coperidingcapplication; Serial NOE? 260,268, :.:;:fi-led December. 6, E1951; I'idesc'ribe novel processes -.eior.'.; continuous :..digestion of wood chips in the manufactureof pulp.

'...This application i :deals with a an i! improved ziistrainer mechanism for .use in wood-pulp digest- .ersgeparticularly digesters used in the-continuous rapu-lpi-ng processes.

:It therefore. a principal-objector my inventitionzto devise adigester-especially ofthe continuczxous: :type": havinga strainer "-afor continuously straining pulp passing therthrough. It is a iurillther Iobject: to provide an-improved means for rzcontinuously backwashing: portions of the strainer ".':in:sucoession without interfering with the opera- .stion-of -the remaini-ngportions thereoffi It is also ,o'aniobject to deviseastrainer having use apart from the digester as shown.

iziFurtherobjects and-advantagesthereoiwill be uiapparentvas the description" -'proceeds and the J. :f-eaturesL-of novelty -will -be pointed out *in the ;claims.

The. usual-strainers empIOyed in' d-igesters conresist-of plates or pip-es: with-a plurality of round 1. :ho1es'"sm'a11 Ienough to prevent -passage of chips huttthroughwhich the liquormay-drainl batch 2-cookingoperationsthese holes gradually become agplugged :fwitir chips and: chip fragments as the a cooking. proceeds; sometimes l'seriously -a-ntrfer- 1 tingiwithsthe'fiow bf thei'circulating liquor." How- I ever; each time theibatchidigester blows i theh'o'les nrgcleaned by. the .rapid movement: of the mass t; ctr/chips .zandzthe reverse. flow :ofsiliquorsandi e zipandingisteam through; the; strainers.

7 Lin; ioontinuous pulping .the: :ohipxi movement is relatively slowiandtthere isno.blowingioperation -.:zto;: clean the4strainer .:p1ates,. i'c'onsequentiy? the wstrainers :tendv to? become; izplugged tighter. and :ctighter.,untiLv thezfiow of liquor. is :seriously. hin- .;dered.

. :The-zimproved; strainer which Lhaveiinvented --:iis;;designed::to=' overcome theseudifiiculties. In- --a .stead.,oignsingg flatiplates or pipes with-ho1es,;I use aiseriesmfv overlapping plates, the-platesrover- (lapping ;in the direction of. flow ilikeishingles .on a;:;house roof. i. The: overlapping i-:p1ates; ;have: a mall:- -;c1earance:.- between their; lapping; surfaces .:.throug11 which;theiliquordrains. '1 Theimotionioi the chips. *tencts tockeep; theseropenings' clean :and aztmsupplement this'J havezprovided a means for :ubaokwashingxthe strainer, xamortion: at a; time; -ior further; cleaning. This :backwashingdaction, grin-addition ;to:sleani-ng :the :strainer;:assistxthe z ehip. movement: toward the discharge sopeningiiof '.-.:the:digester. I

- ,digester :eqnipped' -."With iimy TiIIIpEOYedi strainer.

: Thestraineriproperrconsists of-anumberiot over- ..lapping; 'preferablyzrconicali. rings? or: funnelslike elements I 10f progressively .decreasingnsize...eas i shown. TheseIareLsupported andiinamtainediin place by a: numberrof: 'radiallys:disposedxbridge ,iplates .Jorspartitions Zaas 'ShOWILCiIiiFiES lkianduz. The rings lzmayn-beattached $02 the bfiidge'iPlBLtGS by means of screws or welding .or'=other; known means. The-bridge plates mayilikewise, if desired, be attached tot-hedigester-wall. =Desi-rab1y. the topmost ringmakes a substantially tight. fit with the digester wall in order to keepthebackwashing water from escaping into the digester. --For the usual purpose of cooking-wood chipsofistandare. size, the edges of'the co'nical'rings may Soverlap a distance Iof from approximately one-half to approximately two inches andibe separated at such region of overlap between approximately one-sixteenth and approximately one-h'alfirich and satisfactory results "obtained.

Itw'ill begapparent 'that' the bridge .S'plates'" 2 divide the, space under the istr'ainer rings into a number 'of'sep'a'rate compartments." At'the bottomof these compartments I. provided a part 40 late ttwhichhas ports'"4 opening into 'each com- 'partment. 'Atthe :center of'the' digester. the'h'ol- "low journal 5 serves as Ithe'fch'ip discharge outlet for the digester and"arounditsoutide"carries a ""rotary" va1ve-meehanism '6" comprising" a valve 5 chamber Gdfor performing"the* backwashina'opstimezinwsaidqport platevas. the: waive-irotates. e drip 6b, as shown in Fig. 4, extends slightly to each side of conduit 6a to prevent by-passing of the liquor flow when the conduit is rotating from one port to the other. It will be noted that as shown the valve 6 is substantially hydraulically balanced as far as thrust is concerned by reason of the annular shape of the valve chamber 60 com municating with the passage 6b.

In operation, the circulating liquor in the digester system travels down through the mass of chips, on through the slots formed by the conical rings l through the ports 4 into upper valve compartment ii and out through liquor outlet 13 and on to the liquor circulating pump for return back to the top of the digester. Part of the circulating liquor after leaving the pump, however, is by-passed back to backwash liquor inlet I4 and into lower valve compartment l2. From here it flows up through conduit Ba into one strainer compartment at a time backwashing the strainer slots, and progressing from one strainer compartment to another as the valve 6 rotates. Where preferred a separate pump can be used to supply the backwash liquor instead of by-passing a portion of the circulating liquor flow for this service.

For the rotary parts I find self-lubricating materials like those composed of or containing graphite to be very satisfactory for bearing sleeves or liners i6 and H.

In Fig. 1 the liquor inlet and outlet connections are for sake of clearness shown in vertical alignment. Actually they would preferably be radially located as Figs. 3, 4 and show.

The assembly which I have illustrated shows the strainer located in the conical bottom of a digester. However such overlapping plate strainer elements could be employed at other places in the digester, with or without the backwash ing feature, without departing from the scope concentric partially nested truncated funnel-like elements with the narrow ends of said elements pointed in the direction of travel of the chips and into the tops of the succeeding elements, the surfaces between said elements in the region of nesting being such as to permit the passage of liquid therefrom to the substantial exclusion of the chips, and means for withdrawing the separated liquid from the digester.

2. The digester according to claim 1 having means for backwashing said strainer, comprising partitions extending substantially in the direction of travel of the chips and dividing the spaces between the strainer and the digester into a plurality of compartments, means for directing a stream of backwashing liquid through a small fraction of said compartments in a direction reverse to that of the normal flow and into the main flow of said chips, together with means for moving said stream-directing means so as to backwash all 01" said compartments in succession without interrupting the straining operation of the remaining compartments.

3. In a digester for continuously cooking wood chips to form pulp, said digcster having means for continuously discharging cooked chips therefrom, a strainer in the path of movement of the chips comprising a series of spaced substantially concentric partially nested truncated funnel-like elements with the narrow ends of said elements pointed in the direction of travel of the chips and into the tops of the succeeding elements, the surfaces between said elements in the region of nesting being such as to permit the passage of liquid therefrom to the substantial exclusion of the chips, and means for withdrawing the separated liquid from the digester, said elements progressively decreasing in size in the direction of travel of the chips.

4. The digester according to claim 3 having means for backwashing said strainer, comprising partitions extending substantially in the direction of travel of the chips and dividing the spaces between the strainer and the digester into a plurality of compartments, means for directing a stream of backwashing liquid through a small fraction of said compartments in a direction reverse to that of the normal flow and into the main flow of said chips, together with means for moving said stream-directing means so as to backwash all of said compartments in succession without interrupting the straining operation of the remaining compartments.

5. The digester according to claim 3, in which said elements overlap each other a distance of approximately one-half inch to approximately two inches and are separated in the region of overlap from approximately of an inch to approximately one-half inch.

6. In a digester for cooking chips to form pulp, said digester having a conical bottom portion together with means for discharging cooked chips therefrom, a strainer in said bottom portion comprising a series of substantially concentric partially nested truncated funnel-like elements pointed in the direction of travel of the chips and decreasing in size in the direction of travel of the chips, the spacing between said elements in the region of nesting being such as to permit the passage of the liquid therethrough to the substantial exclusion of the chips, the topmost of said elements making a substantially water-tight fit with the digester wall whereby the space between said strainer and the conical bottom portion constitutes a filtrate-receiving chamber, together with means for withdrawing such filtrate from said chamber.

7. A strainer for separating a liquid from solid material, comprising a casing, a series of substantially concentric partially nested truncated funnel-like elements with the narrow ends of said elements pointed in the direction of travel of said material and into the tops of the succeeding elements, the spaces between said elements in the region of nesting being such as to permit the passage of liquid therethrough to the substantial exclusion of the solid material, means for withdrawing the separated liquid from the casing, and means for withdrawing the solid material from the last of said elements.

8. The strainer according to claim 7 having means for backwashing the same, comprising partitions extending substantially in the direction of the material to be strained and dividing the space between the strainer and the casing in a plurality of compartments, and means for directing a stream of backwashing liquid through Number a small fraction of said compartments in a di- 430,595

rection reverse to that of the normal flow and 1,615,609

into the stream of the material to be strained 2,077,074

together with means for moving said stream- 5 2,198,587

directing means so as to backwash all of said 2,451,073

compartments in succession without interrupting the straining operation of the remaining components. Number References Cited in the file Of this patent UNITED STATES PATENTS Number Name Date Tompkins June 17, 1890 Bailey et a1 Jan. 25, 1927 Schneible Apr. 13, 1937 Skinner Apr. 23, 1940 Cowherd -Oct. 12, 1948 FOREIGN PATENTS Country Date Norway June 15, 1936 

1. IN A DIGESTER FOR CONTINUOUSLY COOKING WOOD CHIPS TO FORM PULP, SAID DIGESTER HAVING MEANS FOR CONTINUOUSLY DISCHARGING COOKED CHIPS THEREFROM, A STRAINER IN THE PATH OF MOVEMENT OF THE CHIPS COMPRISING A SERIES OF SPACED SUBSTANTIALLY CONCENTRIC PARTIALLY NESTED TRUNCATED FUNNEL-LIKE ELEMENTS WITH THE NARROW ENDS OF SAID ELEMENTS POINTED IN THE DIRECTION OF TRAVEL OF THE CHIPS AND INTO THE TOPS OF THE SUCCEEDING ELEMENTS, THE SURFACES BETWEEN SAID ELEMENTS IN THE REGION OF NESTING BEING SUCH AS TO PERMIT THE PASSAGE OF LIQUID THEREFROM TO THE SUBSTANTIAL EXCLUSION OF THE CHIPS, AND MEANS FOR WITHDRAWING THE SEPARATED LIQUID FROM THE DIGESTER. 